A known seat slide apparatus for a vehicle includes a pair of lower rails, which are fixed to a vehicle floor via attachment brackets, and a pair of upper rails, which are movably arranged to the lower rails and to which a vehicle seat is attached. Further, the vehicle seat includes a seat belt for securely restraining an occupant to the seat.
An upper belt anchorage and lower belt anchorages for supporting corresponding end portions of the seat belt are usually arranged at a body frame of the vehicle. On the other hand, the upper belt anchorage and the lower belt anchorages may be provided at a rear portion of the seat frame in order to achieve, for example, free movement of the vehicle seat, thereby a belt-integrated seat is provided. In a case where the vehicle is hit, an inertia force is applied to the occupant, and the seat belt is drawn in a front direction of the vehicle by means of a tension force. Consequently, a large load is applied to the upper and lower belt anchorages, and a moment is applied to the seat frame. In other words, a detachment load for detaching the rear portion of the seat frame from a vehicle floor in an upper direction may be generated. Accordingly, in regard to safety, it may be important to increase a resistance load of the seat slide apparatus, which supports the seat frame, relative to the detachment load.
According to JPH07-009694Y, an attachment configuration of a seat adjustor includes a lower hook, which is fixed to a lower rail, and an upper hook, which is fixed to an upper rail to be engageable with the lower hook. When a detachment load is applied from belt anchorages to the upper rail, the lower hook and the upper hook engage with each other so as to bear the detachment load.
The upper hook and the lower hook are arranged to the upper rail and the lower rail, respectively, so as to protrude from horizontal walls of the upper rail and the lower rail, respectively, in a width direction of the vehicle. The lower hook and the upper hook engage with each other at an outside of a cross-sectional area formed by the upper and lower rails.
A position where the lower and upper hooks engage with each other is displaced relative to a bottom wall portion of the lower rail, at which an attachment bracket is fixed, in a horizontal direction. Therefore, when the detachment load is applied to the upper rail, a large bending moment may be applied to the lower rail. Accordingly, it may be difficult to increase a resistance load. Further, since the lower and upper hooks are provided at the outside of the cross-sectional area formed by the lower and upper rails, a size of a seat adjustor may be enlarged.
On the other hand, according to JP2002-154354A, an upper hook and a lower hook are arranged at an inside of a cross-sectional area formed by an upper rail and a lower rail. When the detachment load is applied to the upper rail, the lower and upper hooks engage with each other at the inside of the cross-sectional area formed by the lower and upper rails. A bottom wall portion of the lower rail, at which an attachment bracket is fixed, and a position where the lower and upper hooks engage with each other are not displaced from each other in a horizontal direction when seen in a planar surface extending orthogonally to a longitudinal direction of the lower rail. Therefore, a resistance load may be increased. Further, the lower and upper hooks are arranged at an inside of the cross-sectional area formed by the lower and upper rails. Therefore, a size of the lower and upper rails may be reduced.
However, according to a configuration disclosed in JP2002-154354A, the lower and upper hooks are arranged at the lower and upper rails, respectively, so as to extend in a longitudinal direction of the lower and upper rails. Therefore, configurations of the lower and upper rails may be complex, and weights thereof may be large. Further, due to a detachment load, the lower and upper hooks may be elastically deformed in a direction where the lower and upper hooks are detached from each other, and the lower and upper hooks may not sufficiently support the detachment load. Accordingly, the detachment of the upper rail may not be effectively restricted.
A need thus exists for a seat slide apparatus for a vehicle, which is not susceptible to the drawback mentioned above.